Figure 8.

Results for the second test image that includes dispersion (figure 1b): (a) shows the mean angle (grey line) and the median angle (solid line) for increasing dividing steps n, and (b) shows the weighted error entropy, E_w. In (a), the mean angle fluctuates and does not stabilize owing to the dispersion, and is, therefore, not suited for identifying a range of appropriate ROI sizes. On the other hand, the median angle initially fluctuates but stabilizes around n = 11, yielding a lower cut-off point (left arrow); is then stable up to n = 24 (upper cut-off point) before it starts to drift away. In the stable range of from n = 11 to n = 24, the n² angles from all ROIs yield an angular distribution representing the orientation of lines in the input image. The weighted error entropy, E_w in (b) shows that after an initial increase the PMFs do not change much until n = 14.